Light source device and method of manufacturing the same

ABSTRACT

The first glass portion and the second glass portion are bonded together via an electrically conductive layer that is in contact with the alkaline glass region.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Patent Application No.2019-171454, filed on Sep. 20, 2019, and Japanese Patent Application No.2019-232870, filed on Dec. 24, 2019, the entire contents of which arehereby incorporated by reference.

BACKGROUND

The present disclosure relates to a light source device that includes alaser diode, and to a method of manufacturing the same.

Applications for light source devices that include a laser diode as alight-emitting device are expanding into various fields. For example,display devices (so-called near-eye displays) having a display sectionat a position near the eyes of a user, e.g., head-mounted displays(HMD), are under development.

A light source device described in PCT Publication No. WO 2017/149573has a structure in which a glass cap having a substantiallyrectangular-parallelepiped outer shape covers a laser diode on asubstrate.

SUMMARY

In the light source device described in PCT Publication No. WO2017/149573, flatness of a light-transmitting portion of the glass capmay deteriorate.

The present disclosure provides a light source device in which alight-transmitting portion of a glass cap can attain improved flatness,and a method of manufacturing the same.

A light source device according to one embodiment of the presentdisclosure includes: a laser diode; a substrate directly or indirectlysupporting the laser diode; and a cap secured to the substrate andcovering the laser diode. The cap includes a first glass portionconfigured to transmit laser light that is emitted from the laser diode,and a second glass portion. At least one of the first glass portion andthe second glass portion includes an alkaline glass region. The firstglass portion and the second glass portion are bonded together via anelectrically conductive layer that is in contact with the alkaline glassregion.

A method of manufacturing a light source device according to oneembodiment of the present disclosure includes: providing a substratedirectly or indirectly supporting a laser diode; providing a cap, thecap including a first portion configured to transmit laser light that isemitted from the laser diode and a second portion, at least one of thefirst portion and the second portion including an alkaline glass region,and the first portion and the second portion being bonded together viaan electrically conductive layer disposed in contact with the alkalineglass region; and covering the laser diode with the cap and securing thecap to the substrate.

According to certain embodiments of the present disclosure, a lightsource device in which a light-transmitting portion of a glass cap canattain improved flatness can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view schematically showing an example structureof a light source device according to one embodiment of the presentdisclosure.

FIG. 1B is a perspective view schematically showing an example structureof a light source device according to one embodiment in manufacturingthereof.

FIG. 2 is a perspective view schematically showing another example of alight source device according to one embodiment of the presentdisclosure.

FIG. 3A is a cross-sectional view of a light source device according toone embodiment as taken parallel to the YZ plane.

FIG. 3B is a cross-sectional view of a light source device according toone embodiment as taken parallel to the XY plane.

FIG. 4A is a cross-sectional view of a light source device according toanother embodiment as taken parallel to the YZ plane.

FIG. 4B is a cross-sectional view of a light source device according toanother embodiment as taken parallel to the XY plane.

FIG. 5A is a cross-sectional view of a light source device according tostill another embodiment as taken parallel to the YZ plane.

FIG. 5B is a cross-sectional view of a light source device according tostill another embodiment as taken parallel to the XY plane.

FIG. 6 is an exploded perspective view of a glass cap according to theembodiment shown in FIG. 5A.

FIG. 7 is a perspective view showing an example of a plate including aplurality of second glass portions.

FIG. 8 is a perspective view of a bar before singulated into a pluralityof glass caps.

FIG. 9 is a diagram schematically showing an upper surface (on the left)and a cross section along line A-A (on the right) of a plate.

FIG. 10 is a diagram schematically showing an upper surface (on theleft) and a cross section along line A-A (on the right) of a platehaving a plurality of depressions arranged in rows and columns.

FIG. 11 is a diagram schematically showing an upper surface (on theleft) and a cross section along line A-A (on the right) of a plate onwhich metal layers are disposed.

FIG. 12 is a diagram schematically showing an upper surface (on theleft) and a cross section along line A-A (on the right) of a plate towhich a first glass sheet is bonded.

FIG. 13A is a cross-sectional view schematically showing forming of anantireflection coating.

FIG. 13B is a cross-sectional view schematically showing forming of anantireflection coating.

FIG. 13C is a cross-sectional view schematically showing forming of anantireflection coating.

FIG. 14 is a diagram schematically showing an upper surface (on theleft) and a cross section along line A-A (on the right) of a panel.

FIG. 15 is a diagram showing singulation from a bar into caps.

FIG. 16 is a cross-sectional view schematically showing an examplestructure of a cap according to a modified example.

FIG. 17 is a cross-sectional view of a light source device including thecap in FIG. 16.

FIG. 18 is an exploded perspective view of a cap according to anothermodified example.

FIG. 19 is a cross-sectional view of the light source device accordingto one modified example shown in FIG. 18, as taken parallel to the YZplane.

FIG. 20 is a diagram schematically showing a partial cross section of aplate 42 and glass sheets 47 and 48 prior to performing anodic bonding.

FIG. 21 is a diagram schematically showing an upper surface (on theleft) and a cross section along line A-A (on the right) of a plate onwhich a lattice of grooves defining recesses are formed.

FIG. 22 is a cross-sectional view schematically showing an examplestructure of a light source device in which a patterned metal layer isdisposed on the cap.

FIG. 23 is a cross-sectional view schematically showing another examplestructure of a light source device in which a patterned metal layer isdisposed on the cap.

FIG. 24 is a cross-sectional view schematically showing a depth D of adent relative to the surface of a thin portion 40Tu serving as a bottomof the dent, a width Wh of grooves to be formed through half-dicing, anda cut width Wf resulting from fully-cutting a panel 50 apart.

DETAILED DESCRIPTION

With reference to FIG. 1A and FIG. 1B, a configuration of a light sourcedevice according to one embodiment of the present disclosure will bedescribed. FIG. 1A is a perspective view schematically showing anexample structure of a light source device 100 according to the presentembodiment. FIG. 1B is a perspective view schematically showing anexample structure of the light source device 100 in manufacturingthereof. In the figures, the X axis, the Y axis, and the Z axis, whichare orthogonal to one another, are shown for reference sake.

The illustrated light source device 100 includes a laser diode 10, asubstrate 30 directly or indirectly supporting the laser diode 10, and acap 40 that is fixed to the substrate 30 and covers the laser diode 10.

The cap 40 defines a recess 40V for accommodating the laser diode 10.When the cap 40 is not fixed to the substrate 30, the recess 40V opensdownward, as shown in FIG. 1B. A frontal portion 40F of the cap 40 islight-transmissive to transmit laser light 14 that is radiated from thelaser diode 10. A surface of the frontal portion 40F facing the laserdiode 10 (i.e., at an inner side) is flat, and may exemplarily besmooth. An antireflection coating may be disposed on an outer surfaceand/or an inner surface of the frontal portion 40F. The cap 40 has alower end surface 40E that is bonded to a principal surface 32 of thesubstrate 30. The lower end surface 40E is located surrounding theopening of the recess 40V. Although the recess 40V has a rectangularparallelepiped shape in the example shown in drawings, the recess 40Vmay have a shape other than a rectangular parallelepiped shape. Theconfiguration of the cap 40 and a method of producing the same will bedescribed below in detail.

Examples of the laser diode 10 include a laser diode that radiates bluelight, a laser diode that radiates green light, and a laser diode thatradiates red light. A laser diode that radiates other light may beemployed.

In the present specification, blue light refers to light having anemission peak wavelength in a range of 420 nm to 494 nm. Green lightrefers to light having an emission peak wavelength in a range of 495 nmto 570 nm. Red light refers to light having an emission peak wavelengthin a range of 605 nm to 750 nm.

Examples of laser diodes that emit blue light or laser diodes that emitgreen light include laser diodes containing a nitride semiconductor.Examples of a nitride semiconductor include GaN, InGaN, and AlGaN.Examples of laser diodes that emit red light include laser diodescontaining an InAlGaP-based or GaInP-based semiconductor, a GaAs-basedor AlGaAs-based semiconductor, etc.

Laser light 14 radiated from the laser diode 10 is divergent, andcreates a far field pattern (hereinafter abbreviated as “FFP”) of anelliptical shape at a surface that is parallel to an emission endsurface through which the laser light 14 is emitted. The FFP isdetermined by an optical intensity distribution of the laser light 14 ata position apart from the emission end surface. In this opticalintensity distribution, a portion having an intensity that is 1/e² orgreater with respect to the peak intensity value may be referred to as a“beam cross section.”

While an edge-emission type laser diode having an end surface throughwhich the laser light 14 is emitted is employed for the laser diode 10in the present embodiment, a surface emitting type laser diode (VCSEL)may be employed for the laser diode 10. For simplicity, a center axis ofthe laser light 14 is indicated with a broken line in the drawing. Theactual laser light 14, as described above, diverges and spreads outafter being emitted through the end surface 12 of the laser diode 10.Therefore, the laser light 14 may be collimated or converged by anoptical system including a lens or lenses, which are not shown. Such anoptical system may be provided outside of the light source device 100.At least a portion of the optical system including lenses forcollimation or convergence may be provided on the cap 40, or disposedwithin the recess 40V of the cap 40.

The center axis of the laser light 14 extends in a direction along theprincipal surface 32 of the substrate 30 (i.e., the Z axis direction).Laser light 14 emitted from the light source device 100 to the outsidemay be reflected in a direction e.g. perpendicular to the principalsurface 32 of the substrate 30 by a mirror disposed outside the lightsource device 100.

In the example shown in drawings, the laser diode 10 is mounted on theprincipal surface 32 of the substrate 30 in a state of being secured ona submount 20. Without utilizing the submount 20, the laser diode 10 maybe directly bonded to the principal surface 32 of the substrate 30instead. In these drawings, a wiring for connecting the laser diode 10to an external circuit is omitted from illustration.

A ceramic may be used for a main material of the substrate 30. For thesubstrate 30, a material other than a ceramic may be used, and a metalmay be used. Examples of a main material of the substrate 30 includeceramics such as aluminum nitride, silicon nitride, aluminum oxide, andcarbon nitride; metals such as copper, aluminum, iron; and compositessuch as copper molybdenum, copper-diamond composite materials, andcopper tungsten.

A plurality of metal layers may be disposed on each of an upper surfaceand a lower surface of the substrate 30. A metal may be disposed toextend inside the substrate 30, which allows metal layers on the uppersurface to be electrically connected to metal layers on the lowersurface. On the lower surface of the substrate 30, metal layers that arenot electrically connected to the metal layers on the upper surface maybe disposed. Examples of the substrate 30 include a multilayered ceramicsubstrate that includes interconnects on the inside and/or the outside.

The submount 20 has a lower surface, an upper surface, and lateralsurfaces, and may exemplarily have a rectangular-parallelepiped shape.The submount 20 may be made of a silicon nitride, an aluminum nitride,or a carbon nitride, for example. Metal layers for connecting the laserdiode 10 to interconnects on the substrate 30 may be disposed on theupper surface of the submount 20.

The cap 40 is secured to the substrate 30 to cover the laser diode 10supported by the substrate 30. In the example in drawings, the lower endsurface 40E of the cap 40 is bonded to the principal surface 32 of thesubstrate 30. Such bonding may be achieved via a layer of inorganicmaterial (e.g. a metal) or organic material. Thus, the laser diode 10may be sealed airtight. The light source device 100 depicted in FIG. 1Amay be referred to as a “semiconductor laser package.” While the exampleshown in drawings illustrates a configuration in which a single lightsource device 100 includes a single laser diode 10, other configurationsmay be employed in embodiments of the present disclosure. A plurality oflaser diodes 10 may be arranged inside a single recess 40V of the cap40. The plurality of laser diodes 10 may be disposed parallel to oneanother, so as to emit the laser light 14 in an identical direction.

FIG. 2 is a perspective view schematically showing another example of alight source device according to one embodiment of the presentdisclosure. In this example, the substrate 30 includes three laserdiodes 10R, 10G and 10B that are arranged on a single submount 20. Thelaser diodes 10R, 10G and 10B respectively radiate laser light 14 ofred, green, and blue colors. The laser diodes 10R, 10G and 10B may behoused inside the single cap 40 and sealed airtight. Two or moresubmounts 20 may be employed, and the submounts 20 are providedseparately for respective ones of the laser diodes 10R, 10G and 10B.

The laser light 14 radiated from each of the laser diodes 10R 10G and10B may be combined into a coaxial beam by a beam combiner not shown.The laser diodes 10R, 10G and 10B may radiate the laser light 14 withrespectively different timings, or all simultaneously. Emission of thelaser light 14 is controlled by a driving circuit not shown.

During operation of the light source device 100, the laser light 14emitted from the laser diode 10 is transmitted through the frontalportion 40F of the cap 40. An antireflection coating may be disposed onan outer side and/or an inner side of the frontal portion 40F. Portionsof the cap 40 other than the frontal portion 40F do not need to belight-transmissive.

Hereinafter, with reference to FIG. 3A and FIG. 3B, an example structureof the cap 40 according to the present embodiment will be described indetail. FIG. 3A is a diagram schematically showing a cross sectionparallel to the YZ plane, the cross section containing the center axisof the laser light 14. FIG. 3B is a cross-sectional view taken alongline 1B-1B in FIG. 3A, showing a cross section that is parallel to theXY plane. FIG. 3A corresponds to a cross-sectional view along line 1A-1Ain FIG. 3B.

The cap 40 in the present embodiment includes a plate-like first portion(first glass portion) 40A that transmits laser light 14 emitted from thelaser diode 10, and a second portion (second glass portion) 40B that ismade of a different material from the first glass portion 40A. The firstglass portion 40A is disposed to intersect with a path of the laserlight 14 on the substrate 30 and is bonded to the substrate 30. As shownin FIG. 3A, the second glass portion 40B includes a plate-like portion40B1, which is disposed parallel to the first glass portion 40A, and aportion 40B2 having a cross section of a shape of the alphabeticalletter “C” as shown in FIG. 3B, such that the portions 40B1 and 40B2 arecontinuous and monolithically formed with each other. As shown in FIG.3B, the portion 40B2 of the second glass portion 40B having the “C”cross section includes: a pair of lateral wall portions 40S that arelocated at a lateral side of the laser diode 10; and a cover portion 40Tthat is located above the laser diode 10 and connects the pair oflateral wall portions 40S together. Thus, the second glass portion 40Bhas a shape defining the recess 40V.

At least one of the first glass portion 40A and the second glass portion40B is made of an alkaline glass. An “alkaline glass” as used herein isa silicate compound glass that contains movable ions of alkali metalelements such as Na⁺, Ka⁺, and/or Li⁺. A silicate compound glasscontaining an alkaline oxide at a concentration of 0.1 mass % or less isreferred to as a “non-alkaline glass.” Examples of silicate compoundglasses include silicate glass, borosilicate glass, and quartz glass.

The first glass portion 40A and the second glass portion 40B are bondedtogether via an electrically conductive layer 40M. In one embodiment,the first glass portion 40A is an alkaline glass that is anodicallybonded to an electrically conductive layer 40M that is disposed on thesurface of the second glass portion 40B. The electrically conductivelayer 40M may be composed of different kinds of metals being stackedupon one another. For example, the electrically conductive layer 40M maybe a layered structure in which a titanium layer as an underlying layeris deposited on the surface of the second glass portion 40B and analuminum layer is deposited on the titanium layer. Materials other thanthose in the example described above may be employed as a material ofthe electrically conductive layer 40M.

Anodic bonding can be carried out by applying a potential (e.g. −500volts to −1 kilovolt) lower than the potential of the second glassportion 40B to the first glass portion 40A, followed by heating at atemperature in a range of about 300° C. to 400° C. For anodic bonding,any appropriate technique may be employed, and various known techniquesmay be employed. As a result of the anodic bonding, the concentration ofthe alkali metal element in the first glass portion 40A is locallydecreased in a region in contact with the electrically conductive layer40M. In this example, the second glass portion 40B may be made of analkaline glass, or made of a non-alkaline glass or a semiconductor(monocrystalline silicon, polycrystalline silicon, carbon nitride,etc.). The second glass portion 40B does not need to belight-transmissive. While the example in FIG. 3A illustrates that theelectrically conductive layer 40M is disposed only at the bondingsurface, the electrically conductive layer 40M may also be formed on asurface (inner surface) of the second glass portion 40B that defines therecess 40V. Specific examples of the method of producing the cap 40 willbe described later.

According to one embodiment of the present disclosure, thelight-transmitting portion (first glass portion 40A) of the cap 40 has aplate shape, so that the first glass portion 40A can easily have asmooth surface. Moreover, it is also possible to form an antireflectioncoating on a surface of the first glass portion 40A, prior to bonding.This allows an antireflection coating to be formed on the inner surfaceof the cap 40 with a high production yield, even if the cap 40 isreduced in size.

Any appropriate configurations other than those in the exampleillustrated in FIG. 3A and FIG. 3B may be employed for the cap 40according to embodiments of the present disclosure. With reference toFIG. 4A and FIG. 4B, another example structure will be described. FIG.4A is a cross-sectional view of the light source device 100 according tothis example structure, as taken parallel to the YZ plane. FIG. 4B is across-sectional view taken along line 1B-1B in FIG. 4A. FIG. 4Acorresponds to a cross-sectional view taken along line 1A-1A in FIG. 4B.

In the example shown in FIG. 4B and FIG. 4A, the second glass portion40B of the cap 40 has a shape in which an inner wall surface includes acurved surface. Thus, the recess 40V of the cap 40 may have shapes otherthan a rectangular parallelepiped shape.

Next, with reference to FIG. 5A and FIG. 5B, still another examplestructure will be described. FIG. 5A is a cross-sectional view of thelight source device 100 according to this example structure, as takenparallel to the YZ plane. FIG. 5B is a cross-sectional view at line1B-1B in FIG. 5A. FIG. 5A corresponds to a cross-sectional view takenalong line 1A-1A in FIG. 5B.

In the example shown in FIG. 5B and FIG. 5A, the cap 40 includes a thirdglass portion 40C facing the first glass portion 40A, with the laserdiode 10 disposed therebetween. As shown in FIG. 5A, the second glassportion 40B connects the first glass portion 40A and the third glassportion 40C together. The second glass portion 40B has a “C”-like shape,as shown in FIG. 5B. At least one of the second glass portion 40B andthe third glass portion 40C is an alkaline glass. In certainembodiments, the third glass portion 40C may be an alkaline glass, andis anodically bonded to an electrically conductive layer 40M disposed onthe surface of the second glass portion 40B. As a result of the anodicbonding, the concentration of the alkali metal element in the thirdglass portion 40C is locally decreased in a region in contact with theelectrically conductive layer 40M. The second glass portion 40B may bemade of an alkaline glass, with each of the first glass portion 40A andthe third glass portion 40C made of a non-alkaline glass. Alternatively,each of the first to third glass portions 40A to 40C may be made of analkaline glass.

As illustrated in FIG. 6, the cap 40 shown in FIG. 5A and FIG. 5B has astructure in which the first glass portion 40A and the third glassportion 40C are disposed on two opposite sides of the second glassportion 40B and are bonded to the second glass portion 40B. The secondglass portion 40B that has been described with reference to FIGS. 3Athrough 4B corresponds to a structure in which the second glass portion40B and the third glass portion 40C shown in FIG. 5A are monolithicallyformed and made of the same glass material.

FIG. 7 is a perspective view schematically showing an example of a plate42 from which a plurality of second glass portions 40B (see FIG. 6) willbe formed. The plate 42 has six through holes 42H that are arranged intwo rows and three columns. The through holes 42H are closed with twoglass sheets 47 and 48 on two opposite sides of the plate 42, so that asingle panel can be obtained. The panel is divided along the lateraldirection in FIG. 7 to obtain bars 60 (one of which is shown in FIG. 8).Three caps can be produced from such a single bar 60.

Hereinafter, one embodiment of a method of efficiently producing amultitude of caps 40 will be described in more detail.

First, see FIG. 9. FIG. 9 is a diagram schematically showing an uppersurface (on the left) and a cross section taken along line A-A (on theright) of the plate 42. The plate 42 has a first surface (upper surface)44 and a second surface (lower surface) 46 opposite to the first surface44. As shown in the drawing, the plate 42 has a plurality of throughholes 42H that are arranged in a two-dimensional array along a firstdirection Dx and along a second direction Dy intersecting the firstdirection Dx, the first direction Dx and the second direction Dyextending in the first surface 44. The through holes 42H extend throughthe first surface 44 and the second surface 46. In this example, thefirst direction Dx is parallel to the X axis, and the second directionDy is parallel to the Y axis. Each through hole 42H extends along the Zaxis direction.

The through holes 42H can be formed by providing a glass orsemiconductor substrate (thickness: e.g. 0.5 to 4 mm), and processingthis substrate, for example. Examples of processing include formation ofa mask pattern, sandblasting, etching, and the like. Using suchprocessing techniques, instead of forming through holes 42H that extendthrough the first surface 44 and the second surface 46, depressions 42Rthat are recessed from the first surface 44 toward the second surface 46can be formed. In the example shown in FIG. 10, after covering the firstsurface 44 of the plate 42 with a mask 45 having openings that determinethe shapes and positions of the depressions 42R, exposed portions of theplate 42 are selectively removed through the openings of the mask 45.The plate 42 in FIG. 10 has a plurality of depressions 42R arranged inrows and columns. The two-dimensional array of the plurality ofdepressions 42R includes a first linear array of depressions 42Rarranged along the first direction and a second linear array ofdepressions 42R arranged along the first direction and adjacent to thefirst linear array of depressions 42R in the second direction.Increasing the depth of the depressions 42R would result in the throughholes 42H. The sizes of the depressions 42R or through hole 42H alongthe X direction, the Y direction, and the Z direction may be,respectively, 1 to 5 mm, 2 to 5 mm, and 0.5 to 4 mm, for example.

Next, FIG. 11 will be described. FIG. 11 shows a metal layer 49M thathas been deposited on the first surface 44 of the plate 42, in which theplurality of through holes 42H are defined. Thereafter, as shown in FIG.12, a first glass sheet (thickness: e.g. 0.2 to 1.0 mm) 47 is bonded tothe first surface 44 of the plate 42, on which the metal layer 49M isformed. Typical examples of the metal layer 49M may include a layer ofaluminum (thickness: e.g. 50 to 1000 nm). The metal layer 49M may bemade of a metal other than aluminum, e.g., titanium. The bonding may beperformed using anodic bonding as described above. Thereafter, anantireflection coating may be disposed on the inner surface of the firstglass sheet 47, from the second surface 46 through the through holes42H. The inner surface of the first glass sheet 47 corresponds to theinner surface of the frontal portion 40F of the cap 40 shown in FIG. 1B.According to the present embodiment, an antireflection coating can beeasily formed inside the cap 40 by using a thin-film depositiontechnique such as sputtering, for example.

FIG. 13A and FIG. 13B are cross-sectional views schematically showingsteps for forming an antireflection coating. In this example, as shownin FIG. 13A, a target 46T of a material to compose the antireflectioncoating is disposed at a side of the plate 42 opposite to the secondsurface 46 of the plate 42. More specifically, the plate 42 is placed ina deposition chamber of a sputtering apparatus, for example. A mask 46Mis disposed between the plate 42 and the target 46T. The mask 46M hasopenings of sizes and positions corresponding to the through holes 42Hof the plate 42. By sputtering the target 46T with a plasma, the targetmaterial will be deposited on the inner walls of the through holes 42Hand the exposed surface of the first glass sheet 47, through theopenings of the mask 46M. Accordingly, as shown in FIG. 13B, anantireflection coating 55 is disposed.

The antireflection coating 55 may be disposed using other techniques.After covering regions of the second surface 46 of the plate 42 otherthan the through holes 42H with a mask, the antireflection coating 55may be disposed from a vapor phase or a liquid phase using analternative thin-film deposition technique. In this case, after theantireflection coating 55 is formed, the mask is removed. In the case inwhich the plate 42 has depressions 42R instead of through holes 42H, apattern corresponding to the antireflection coating 55 may be formed onthe first glass sheet 47 prior to bonding.

FIG. 13C is a cross-sectional view schematically showing bonding thefirst glass sheet 47, on which the antireflection coating 55 of apredetermined pattern is formed, to the first surface 44 of the plate42. The first glass sheet 47 is provided with the antireflection coating55, which has been patterned so as to have shapes and sizescorresponding to the plurality of depressions 42R, on a surface of thefirst glass sheet 47. In the illustrated example, an additional singlecontinuous antireflection coating 55 with a uniform thickness is alsoformed on a front surface of the first glass sheet 47. The first glasssheet 47 with an antireflection coating disposed on its front side mayalso be employed in the method that has been described with reference toFIG. 13A and FIG. 13B. Formation of the antireflection coating on thefront side of the first glass sheet 47 may be performed subsequently tocompletion of the anodic bonding.

Next, anodic bonding is performed under conditions similar to the anodicbonding conditions described above, so that a second glass sheet(thickness: e.g. 0.2 to 1.0 mm) 48 is bonded onto the second surface 46of the plate 42, on which the metal layer 49M is formed. In this manner,a panel 50 having a plurality of recesses 40V as shown in FIG. 14 isobtained. For simplicity, the antireflection coating 55 is omitted fromillustration. In the case in which the plate 42 is made of asemiconductor, e.g., silicon, for example, the metal layer 49M is notneeded.

Next, the panel 50 is cut along the first direction Dx. Morespecifically, the panel 50 is cut in order to divide the panel 50 into aplurality of bars 60 such that a first cutting plane C1 extends across afirst linear array of through holes (recesses 40V) arranged along thefirst direction Dx and that a second cutting plane C2 parallel to thefirst cutting plane C1 extends across a region between the first lineararray of through holes (recesses 40V) and a second linear array ofthrough holes (recesses 40V) arranged along the first direction Dx andadjacent to the first linear array of through holes (recesses 40V) alongthe second direction Dy. Dividing may be performed by using a dicingsaw, for example.

In the upper row of FIG. 15, two bars 60 that have been separated at thefirst cutting plane C1 are schematically shown. As shown in the lowerdrawing of FIG. 15, by cutting each bar 60 along the second directionDy, in a region between adjacent through holes (recesses 40V) adjoiningalong the first direction Dx, a plurality of singulated caps 40 can beobtained from each bar 60. Each cap 40 is divided along a third cuttingplane C3. The glass sheets 47 and 48 are not illustrated in FIG. 15. Thelower end surface, the upper surface, and the lateral surfaces of eachcap 40 are created by cutting along the cutting planes C1, C2 and C3,respectively, while surfaces of each cap 40 that are parallel to theplane shown in the drawing are defined by the glass sheets 47 and 48(see FIG. 14). Surfaces created by cutting along the cutting planes C1,C2 and C3 may have irregularities that results from dicing or otherprocessing. On the other hand, laser light will be transmitted throughthe smooth portion that is created from the first glass sheet 47, andtherefore is free from adverse effects of the cut surfaces. Thus,according to the present embodiment, flatness and smoothness of thefirst glass sheet 47 are not degraded through the manufacturing, so thatlaser light is transmitted through a portion of the cap 40 that has goodsmoothness. In the case in which the surfaces created by cutting alongthe cutting planes C1, C2 and C3 have irregularities, irregularities maybe flattened by polishing or the like. In particular, a bonding surfacewith the supporting substrate is preferably flat.

In this manner, a multitude of caps 40 each having a configuration shownin FIG. 5A and FIG. 5B can be produced. The first glass portion 40A andthe third glass portion 40C of each cap 40 are made of, respectively, aportion of the first glass sheet 47 and a portion of the second glasssheet 48, while the second glass portion 40B is made of a portion of theplate 42. Moreover, each of the electrically conductive layers 40M ismade of a corresponding portion of the metal layer 49M.

Using the plate 42 in the state shown in FIG. 10 allows for forming amultitude of caps 40 each having the configuration shown in FIG. 3A andFIG. 3B. In that case, the first glass portion 40A of each cap 40 ismade of a portion of the first glass sheet 47, and the second glassportion 40B is made of a portion of the plate 42. The electricallyconductive layer 40M is made of a portion of the metal layer 49M.

Using the cap 40 thus produced, the light source device 100 shown inFIG. 1A can be obtained.

According to one embodiment of the present disclosure, it is possible tomass-produce caps 40 having a height (size along the Y direction) ofe.g. 2 millimeters or less. Moreover, an antireflection coating can beappropriately formed on the cap 40, so that transmittance of laser lightcan be enhanced, and stray light can be reduced.

Hereinafter, example modifications to the embodiment described abovewill be described.

While the embodiment described above illustrates a configuration inwhich at least one of the first glass portion 40A and the second glassportion 40B is an alkaline glass, it is not necessary for the entirefirst glass portion 40A or the entire second glass portion 40B to be analkaline glass. More specifically, at least one of the first glassportion 40A and the second glass portion 40B may include an alkalineglass region, and the first glass portion 40A and the second glassportion 40B may be bonded together via an electrically conductive layer40M that is in contact with that alkaline glass region included in theat least one of the first glass portion 40A and the second glass portion40B.

In a configuration in which the cap 40 includes the third glass portion40C facing the first glass portion 40A such that the laser diode 10 isdisposed between the third glass portion 40C and the first glass portion40A, and the second glass portion 40B connects the first glass portion40A and the third glass portion 40C together, at least one of the secondglass portion 40B and the third glass portion 40C may include analkaline glass region, and the second glass portion 40B and the thirdglass portion 40C may be bonded together via an electrically conductivelayer 40M that is in contact with that alkaline glass region.

With reference to FIG. 16 and FIG. 17, a modified example of the presentdisclosure will be described. FIG. 16 is a cross-sectional viewschematically showing an example structure of the cap 40 according tothe modified example. FIG. 17 is a cross-sectional view of a lightsource device 100 including the cap 40 according to the modifiedexample. The cap 40 shown in FIG. 16 includes a first glass portion 40A,a second glass portion 40B, and a third glass portion 40C. The firstglass portion 40A includes an alkaline glass region 70A and anon-alkaline glass region 72A that is connected to the alkaline glassregion 70A. The third glass portion 40C includes an alkaline glassregion 70C and a non-alkaline glass region 72C that is connected to thealkaline glass region 70C. The second glass portion 40B in this exampleincludes a non-alkaline glass region 70B, but does not include analkaline glass region. Alternatively, the second glass portion 40B mayinclude an alkaline glass region that is in contact with an electricallyconductive layer 40M.

In the example of FIG. 16, the non-alkaline glass region 72A and thenon-alkaline glass region 72C both have a thin plate shape. The alkalineglass region 70A and the alkaline glass region 70C are disposed atpredetermined positions of the non-alkaline glass region 72A and thenon-alkaline glass region 72C, respectively. A blank arrow on the leftside of FIG. 16 schematically indicates that the alkaline glass region70A of the first glass portion 40A is bonded to an electricallyconductive layer 40M of the second glass portion 40B. Similarly, a blankarrow on the right side of FIG. 16 schematically indicates that thealkaline glass region 70C of the third glass portion 40C is bonded to anelectrically conductive layer 40M of the second glass portion 40B. Suchbonding is performed through the anodic bonding described above. Inorder to produce the cap 40 having such a structure, the alkaline glassregion 70A may be provided in a region of the glass sheet 47 in FIG. 14facing the first surface 44 of the plate 42. Similarly, the alkalineglass region 70C may be disposed in a region of the glass sheet 48 inFIG. 14 facing the second surface 46 of the plate 42. As can be seenfrom the left-hand side diagram in FIG. 14, the first surface 44 and thesecond surface 46 of the plate 42 have a lattice shape extending acrossthe YX plane. Accordingly, it is desirable that the alkaline glassregions 70A and 70C also have a lattice shape extending across the YXplane on the glass sheets 47 and 48.

In order to produce the cap 40 through anodic bonding, it is sufficientthat an alkaline glass region exists in a portion in contact with ametal layer used for anodic bonding, and it is not necessary that theentire glass portion located on either side of the metal layer used foranodic bonding is made of an alkaline glass.

Next, another modified example will be described with reference to FIG.18 to FIG. 23.

FIG. 18 and FIG. 19 will next be described. FIG. 18 is an explodedperspective view of the cap 40 according to this modified example. FIG.19 is a cross-sectional view of the light source device 100 according tothis modified example as taken parallel to the YZ plane.

In the modified example of FIG. 18, the second glass portion 40B of thecap 40 includes a thin portion 40Tu in the cover portion 40T and thinportions 40Su in the lateral wall portions 40S. More specifically, thesecond glass portion 40B includes: the thin portions 40Tu and 40Su; athick portion 40Ta that has a thickness greater than a thickness of thethin portion 40Tu; and thick portions 40Sa that have a thickness greaterthan a thickness of the thin portions 40Su. A thickness of each of thethin portion 40Tu and the thick portion 40Ta refers to a size of acorresponding portion of the cover portion 40T along the Y axisdirection. A thickness of each of the thin portions 40Su and A thicknessof each of the thick portions 40Sa refer to sizes of respectivecorresponding portions of each lateral wall portion 40S along the X axisdirection.

As shown in FIG. 19, the difference between a thickness of the thinportion 40Tu and a thickness of the thick portion 40Ta is, for example,10 μm or greater and 200 μm or less. The difference between a thicknessof the thin portions 40Su and a thickness of the thick portions 40Sa canbe in a similar range. A method of forming the thin portions 40Tu and40Su will be described below.

The cap 40 according to these modified examples can be producedgenerally using a method similar to the method that has been describedwith reference to FIG. 9 to FIG. 15, except that, prior to performingthe anodic bonding, portions of the plate 42 are removed from the firstsurface (upper face) 44 of the plate 42 to form the thin portions 40Tuand 40Su.

FIG. 20 is a diagram schematically showing a partial cross section ofthe plate 42 and the glass sheets 47 and 48 prior to performing anodicbonding. At the portions of the plate 42 where the through holes 42H arelocated, the first surface 44 and the second surface 46 are indicated asdotted lines. The thin portions 40Tu and 40Su may be formed byprocessing (half-dicing) the plate 42 using dicing technique, andforming a lattice-shaped grooves, which are shallower than the thicknessof the plate 42, in the first surface 44 of the plate 42. Thelattice-shaped grooves are formed to pass through the cutting planesused when the caps 40 are singulated. The lattice-shaped grooves canhave a depth, i.e., size along the Z direction, of, for example, 30% orgreater and 70% or less of a thickness of the plate 42. The grooveformed by the half-dicing can have a width (i.e., size of each groovealong the Y direction or the X direction) in a range of, for example, 50μm to 3 mm.

FIG. 21 shows the glass sheets 47 and 48 that have been bonded to theplate 42 in which the lattice-shaped grooves are formed. Thelattice-shaped grooves that have been formed through a half-dicinginclude a plurality of first grooves 40Tx extending along the X axisdirection and a plurality of second grooves 40Sy extending along the Yaxis direction. By dividing the panel 50 in FIG. 21 produced throughanodic bonding, the cap 40 according to this modified example can beobtained. The method for dividing the panel 50 may be similar to that inthe method described with reference to FIG. 15.

According to this modified example, when the panel 50 is divided, thelattice-shaped grooves defining the first and second grooves 40Tx and40Sy exist along the splitting lines. At portions with the first andsecond grooves 40Tx and 40Sy, a thickness of the plate 42 is reduced,which facilitates cutting. Therefore, when the panel 50 is divided bydicing or the like, breaking or chipping of the panel 50 can be reduced.As a result, the shape of each individual cap 40 is not degraded, sothat the percentage of non-defective products, that is production yieldis improved.

FIG. 22 is a cross-sectional view schematically showing an examplestructure of a light source device 100 in which a patterned metal layer(a metal layer pattern) 80 is disposed on the upper surface of the cap40, more specifically, on the surface of the thin portion 40Tu, usingthe thin portion 40Tu of the cap 40. The metal layer 80 contains apattern that is visually identifiable to humans, e.g., text characters,diagrams, and/or symbols, or a pattern that is decodable to electricmachines, e.g., a bar code. These patterns may contain identificationinformation that is assigned to each individual light source device 100,information concerning the production lot, an alignment pattern, a clockpattern, or various other information. The patterned metal layer 80 mayfunction as, for example, an optical mark such as a linear bar code, a2D bar code, or a Data Matrix code.

In a certain embodiment, the metal layer 80 may be deposited at the sametime as depositing a corresponding one of the electrically conductivelayers 40M used for anodic bonding onto the second glass portion 40B ofthe cap 40. The metal layer 80 thus deposited has a layer structure thatis identical to the layer structure of the electrically conductive layer40M. Patterning of the metal layer 80 may be conducted using lift-offtechnique, or a laser marking technique or an etching technique.Depositing the electrically conductive layer 40M and the metal layer 80in the same step allows for efficiently forming marks includingidentification information. While the example of FIG. 22 illustrates themetal layer 80 being deposited on the surface of the thin portion 40Tuand thus being formed on the upper surface of the cap 40, the metallayer 80 may be disposed on the other thin portions 40Su. Disposing themetal layer 80 on the bottom surface of a recessed portion of the cap 40allows for preventing forming an unnecessary protrusion by the metallayer 80, thus allowing the outer periphery of the cap 40 to be locatedwithin a predetermined accommodation space.

The recessed portion formed with a surface of the thin portion 40Tu and40Su serving as a bottom of the recessed portion has a depth D narrowerthan a half of a width Wh of the grooves to be formed by the half-dicingdescribed above. More specifically, given a cut width Wf resulting fromfully-cutting the plate 42 apart, a relationship D=(Wh−Wf)/2 can beapproximately satisfied. For example, the depth D is in a range of about10 to 200 μm. Therefore, the recessed portion of the cap 40 where themetal layer 80 is disposed can be obtained by setting the width Wh ofthe grooves formed through half-dicing to be greater than the cut widthmade in the plate 42 when cutting along the second cutting plane C2, forexample. FIG. 24 is a cross-sectional view schematically showing thedepth D of the recessed portion formed with the surface of the thinportion 40Tu serving as a bottom of the recessed portion, the width Whof grooves formed through half-dicing, and the cut width Wf when thepanel 50 is fully cut apart. In the case in which the cutting planes C1and C2 for the full-cut are formed using a blade, for example, the cutwidth Wf corresponds to the blade width.

In FIG. 21, the groove width of the first grooves 40Tx through which thefirst cutting plane C1 extends and the groove width of the first grooves40Tx through which the second cutting plane C2 extends are representedin the same size. The groove width of the first grooves 40Tx throughwhich the first cutting plane C1 extends is preferably equal to or lessthan the cut width resulting from dividing of the panel 50. The firstcutting plane C1 is a surface defining the lower end surface 40E of thecap 40 (see FIG. 15). As shown in FIG. 18, the lower end surface 40E ofthe cap 40 is bonded to the principal surface 32 of the substrate 30,and accordingly is preferably flat. Therefore, when performinghalf-dicing to form the first grooves 40Tx at cut surfaces created bycutting along the first cutting plane C1, the groove width Wh resultingfrom the half-dicing is preferably equal to or less than the cut widthWf resulting from fully-cutting the plate 42 apart. Even ifirregularities resulting from half-dicing exists on the cut surfacescreated by cutting along the first cutting plane C1, the cut surfacesmay be flattened by performing polishing or the like after the cutting.

FIG. 23 is a cross-sectional view schematically showing another examplestructure of the light source device 100, in which a patterned metallayer 80 is disposed on the thin portion 40Tu of the cap 40. In thisexample, the cap 40 is obtained by, after producing the plate 42 usingthe method described with reference to FIG. 10, forming a lattice-shapedgrooves defining the thin portions 40Tu and 40Su on the plate 42.

Each of FIG. 22 and FIG. 23 shows the antireflection coating 55 formedon the first glass portion 40A of the cap 40. In these examples, theantireflection coating 55 is formed not only inside, but also outside ofthe first glass portion 40A functioning as the frontal portion 40F ofthe cap 40. The antireflection coating 55 may be disposed on a locationother than that in the illustrated examples.

A light source device according to certain embodiments of the presentdisclosure includes a cap including light-transmitting portion of goodsmoothness and being appropriate for downsizing, and therefore ispreferably used as a small-sized light source for a head-mounted displayor the like. A method of manufacturing a light source device accordingto certain embodiments of the present disclosure allows for an efficientmass production of such a cap, and therefore can reduce the productioncost for a light source device that includes the laser diode.

It is to be understood that although certain embodiments of the presentinvention have been described, various other embodiments and variantsmay occur to those skilled in the art that are within the scope andspirit of the invention, and such other embodiments and variants areintended to be covered by the following claims.

What is claimed is:
 1. Alight source device comprising: a laser diode; asubstrate directly or indirectly supporting the laser diode; and a capsecured to the substrate and covering the laser diode, the capcomprising: a first glass portion configured to transmit laser lightthat is emitted from the laser diode, and a second glass portion;wherein: at least one of the first glass portion and the second glassportion comprises an alkaline glass region; the first glass portion andthe second glass portion are bonded together via an electricallyconductive layer that is in contact with the alkaline glass region; andthe first glass portion is bonded to the substrate.
 2. The light sourcedevice according to claim 1, wherein: at least one of the first glassportion and the second glass portion is an alkaline glass.
 3. The lightsource device according to claim 1, wherein: the first glass portion isan alkaline glass; and a concentration of an alkali metal element in thefirst glass portion is locally decreased in a region in contact with theelectrically conductive layer.
 4. The light source device according toclaim 1, wherein: the first glass portion comprises the alkaline glassregion and a non-alkaline glass region that is connected to the alkalineglass region.
 5. The light source device according to claim 1, wherein:the laser diode is an edge-emission type laser diode having an endsurface through which the laser light is emitted, and is mounted on thesubstrate so as to emit the laser light in a direction along thesubstrate; the first glass portion is disposed at a position on thesubstrate such that the first glass portion intersects a path of thelaser light; and the second glass portion comprises: a pair of lateralwall portions that are located at a lateral side of the laser diode, anda cover portion that is located above the laser diode and connects thepair of lateral wall portions together.
 6. The light source deviceaccording to claim 5, wherein: the cap comprises a third glass portionthat faces the first glass portion with the laser diode disposed betweenthe first glass portion and the third glass portion; and the secondglass portion connects the first glass portion and the third glassportion together.
 7. The light source device according to claim 6,wherein: at least one of the second glass portion and the third glassportion comprises an alkaline glass region; and the second glass portionand the third glass portion are bonded together via an additionalelectrically conductive layer that is in contact with the alkaline glassregion.
 8. The light source device according to claim 7, wherein: thethird glass portion comprises the alkaline glass region and anon-alkaline glass region that is connected to the alkaline glassregion.
 9. The light source device according to claim 7, wherein: thesecond glass portion comprises the alkaline glass region and anon-alkaline glass region that is connected to the alkaline glassregion.
 10. The light source device according to claim 6, wherein: thesecond glass portion and the third glass portion are monolithicallyformed and made of a same glass material.
 11. The light source deviceaccording to claim 1, wherein: the second glass portion of the capcomprises a thin portion and a thick portion that has a thicknessgreater than a thickness of the thin portion; and the cap comprises ametal layer pattern on a surface of the thin portion.
 12. The lightsource device according to claim 11, wherein: the metal layer pattern isa bar code or a Data Matrix code.
 13. A method of manufacturing a lightsource device, comprising: providing a substrate directly or indirectlysupporting a laser diode; providing a cap comprising a first portionconfigured to transmit laser light that is emitted from the laser diode,and a second portion, wherein at least one of the first portion and thesecond portion comprises an alkaline glass region, and wherein the firstportion and the second portion are bonded together via an electricallyconductive layer disposed in contact with the alkaline glass region; andcovering the laser diode with the cap and securing the cap to thesubstrate.
 14. The manufacturing method according to claim 13, wherein:the step of providing the cap comprises: providing a plate having afirst surface and a second surface that is opposite to the firstsurface, the plate having a plurality of through holes arranged in atwo-dimensional array along a first direction and along a seconddirection that intersects the first direction, the first direction andthe second direction extending in the first surface, the plurality ofthrough holes extending through the first surface and the secondsurface, the two-dimensional array comprising a first linear array ofthrough holes arranged along the first direction and a second lineararray of through holes arranged along the first direction and adjacentto the first linear array of through holes in the second direction,disposing a metal layer on each of the first surface and the secondsurface of the plate, bonding a first glass sheet to the first surfaceof the plate using anodic bonding, and bonding a second glass sheet tothe second surface of the plate, to produce a panel having a pluralityof recesses, cutting the panel in the first direction along a firstcutting plane and a second cutting plane parallel to the first cuttingplane to obtain a plurality of bars, such that the first cutting planeextends across the first linear array of through holes and the secondcutting plane extends across a region between the first linear array ofthrough holes and the second linear array of through holes, and cuttingeach of the plurality of bars along the second direction betweenadjacent ones of the through holes adjoining along the first directionto singulate the bar into a plurality of the caps, the first portion ismade of a portion of the first glass sheet; the second portion is madeof a portion of the plate; and the electrically conductive layer is madeof a portion of the metal layer.
 15. The manufacturing method accordingto claim 14, wherein: the plate is made of an alkaline glass; and eachof the first and second glass sheets is made of a non-alkaline glass.16. The manufacturing method according to claim 14, wherein: the plateis made of a non-alkaline glass or a semiconductor; and each of thefirst and second glass sheets is made of an alkaline glass.
 17. Themanufacturing method according to claim 14, wherein: the first glasssheet comprises the alkaline glass region and a non-alkaline glassregion that is connected to the alkaline glass region; and in thebonding of the first glass sheet to the first surface of the plate usingthe anodic bonding, the alkaline glass region of the first glass sheetis brought into contact with the metal layer.
 18. The manufacturingmethod according to claim 13, wherein: the step of providing the capcomprises: providing a plate having a first surface and a second surfaceopposite to the first surface, the plate having a plurality ofdepressions arranged in a two-dimensional array along a first directionand along a second direction that intersects the first direction, thefirst direction and the second direction being in the first surface, theplurality of depressions recessed from the first surface toward thesecond surface, the two-dimensional array comprising a first lineararray of depressions arranged along the first direction and a secondlinear array of depressions arranged along the first direction andadjacent to the first linear array of depressions in the seconddirection, disposing a metal layer on the first surface of the plate,bonding a glass sheet to the first surface of the plate using anodicbonding to produce a panel defining a plurality of recesses, cutting thepanel in the first direction along a first cutting plane and a secondcutting plane parallel to the first cutting plane to obtain a pluralityof bars, such that the first cutting plane extends across the firstlinear array of depressions and the second cutting plane extends acrossa region between the first linear array of depressions and the secondlinear array of depressions, and cutting each of the plurality of barsalong the second direction between adjacent ones of the depressionsadjoining along the first direction to singulate the bar into aplurality of the caps; the first portion is made of a portion of theglass sheet; the second portion is made of a portion of the plate; andthe electrically conductive layer is made of a portion of the metallayer.
 19. The manufacturing method according to claim 14, wherein: thestep of providing the cap comprises, before the cutting of the panel toobtain the plurality of bars, performing a half-dicing to form a grooveat a portion of the plate where the second cutting plane is to becreated, the groove being shallower than a thickness of the plate; and awidth of the groove is greater than a cut width made in the plate whencutting along the second cutting plane.
 20. The manufacturing methodaccording to claim 19, further comprising: after the performinghalf-dicing, disposing a metal layer pattern on a surface of the grooveformed in the plate.